Bundle Branch Block Research Articles

Electrophysiological Characteristics and Mechanism of His-Bundle Pacing Guided by Electrocardiograms in Uninterrupted Real-Time Monitoring Technique.

His-bundle pacing (HBP) is a pacing mode that provides near-physiological pacing and has more advantages over standard right ventricle (RV) septum pacing in positive clinical results. However, traditional HBP cannot accurately and stably place the lead tip into the His-Purkinje system. Hence, this study aimed to establish a novel strategy for HBP to strike a balancebetween an excellent pacing threshold and minor injuries to the conduction system. HBP, using continuous and real-time monitoring of unipolar His-bundle (HB) electrograms along with electrocardiograms, was performed in 29 consecutive atrial fibrillation patients. We analyzed the unipolar HB intracardiac electrogram (EGM) and electrophysiological characteristics during HBP using John Jiang's connecting cable and an electrophysiology recording system. All patients were followed up for 12 months. Of the 29 patients, 28 (96.55%) successfully received HBP. Twenty-one (75%) patients were confirmed to have the negative deflection of His potential with a negative amplitude of ≥ 0.1mV in HB EGM. The subgroup with a deep negative deflection was recorded with an HBP threshold (0.71 ± 0.41V), significantly lower than those thresholds with no deep negative deflection (1.83 ± 0.76V) (p < 0.05). The selective HBP rate was significantly different between the two groups: 20 (95.24%) in the deep negative deflection group and three (42.86%) in thenon-deep negative deflection group (p < 0.05); five (17.24%) patients presented right bundle branch block (RBBB) during the lead placement. This study supports the safety and feasibility of using an uninterrupted real-time monitoring technique for HBP. An uninterrupted real-time monitoring technique can guide theaccurate placement of the HB lead and may provide abalancebetween anexcellent pacing threshold and minor injury to the conduction system.

The Significance of rS Change in the V2 Lead for Diagnosing Ventricular Tachycardia Deserves Attention: A Case Report

Abstract Occasionally, incessant ventricular tachycardia (VT) exhibits a narrow QRS complex pattern that could be misdiagnosed as supraventricular tachycardia. In this case, a 66-year-old woman was referred to the emergency department due to the worsen hemodynamic and incessant VT manifesting as a narrow QRS complex pattern that was initially misdiagnosed as supraventricular tachycardia (SVT), which was unresponsive to antiarrhythmic drugs. The electrocardiogram manifestation of VT was characterized by an rS configuration in lead V2 with Rs pattern in leads V1 and V3, and the R-wave amplitude of lead V1 and V3 was greater than that of lead V2, which was different from the typical electrocardiogram features of right bundle branch block. The patient was subsequently found to have suspected acute myocarditis when the cause of the disease was investigated. A combination of high-dose methylprednisolone, immunoglobulin and intra-aortic balloon pump was given immediately. Hemodynamics gradually stabilized, and ventricular tachycardia did not recur. The rS change in the V2 lead may be helpful to distinguish VT from supraventricular tachycardia.

Electrocardiographic strain and relationship with LV remodelling and clinical outcomes in patients with aortic stenosis undergoing transcatheter aortic valve implantation.

Left ventricular (LV) remodelling and fibrosis is known to occur in patients with aortic stenosis (AS) and is linked to post-intervention outcomes. These myocardial changes may be detected upon the routine 12-lead electrocardiogram by the presence of a LV strain pattern (LVS-ECG). Although LVS-ECG has been related to excessive cardiovascular morbidity and mortality in multiple patient populations, there is currently a dearth of data upon its impact in patients undergoing transcatheter aortic valve implantation (TAVI). The aim of the current study was to investigate the prevalence, predictors and prognostic value of LVS-ECG. Between 2012 and 2019, 640 consecutive patients underwent TAVI at Haukeland University Hospital, Bergen. Of these, 600 patients with severe AS were included in the TAVI-NOR study. Patients with known bundle branch block (n=85) or permanent pacing (n=25) were excluded, leaving 490 patients (mean age 81±6years, 52% females) eligible for the analyses. LVS-ECG was defined as down-sloping, convex ST-segment depression with asymmetric T-wave inversion in V5 or V6. LVS-ECG was present in 25.7% patients. Higher levels of NT-proBNP (OR 1.96; 95% CI:1.08-3.55, p=0.028), LVEF<50% (OR 3.14; 95% CI:1.61-6.13, p=0.001), increase in LV mass index per SD (32g/m2) (OR 1.37; 95 CI:1.06-1.76, p=0.014), and the presence of LV hypertrophy on ECG (OR 3.23; 95% CI:1.97-5.32, p<0.001) were independent predictors of LVS-ECG in the multivariable-adjusted analysis. Although all-cause mortality was significantly higher in patients with LVS-ECG compared to those without (54.8% vs 44.2%, p=0.041), the presence of LVS-ECG did not predict all-cause mortality during a median follow-up of 64±24 months (HR 1.05; 95% CI:0.79-1.39, p=0.742). Patients with LVEF <50% and concomitant LVS-ECG had a worse prognosis than those with LVEF >50% and no LVS-ECG (p<0.001). LVS-ECG may represent a simple marker of structural and functional LV remodelling that signals a propensity to excess mortality during long-term follow-up after TAVI, as it is strongly associated with other prognosticators such as reduced LVEF and increased levels of NT-proBNP.

Abstract 4137695: Bundle Branch Block(BBB) is Independently Associated With Adverse Cardiovascular Outcomes in Patients With Heart Failure With Preserved Ejectionfraction(HFPEF): A Propensity Score Matched Analysis

Background: Ventricular dyssynchrony due to BBB can cause adverse cardiovascular(CV) outcomes in HF with reduced EF and is known to occur in HFpEF but its independent impact on is unclear. Objective: To determine if BBB is an independent risk factor for adverse HF outcomes in HFpEF and the impact of atrial fibrillation (AF).. Methods: We studied the impact of BBB in HFpEF utilizing propensity score(PS) matched cohorts without and with BBB from the TOPCAT Americas trial to account for confounding by other co-morbidities. Outcomes analyzed included the TOPCAT primary outcome, CV death&amp;hospitalization (CVH), sudden death, pump failure death (PFD), HF hospitalizations(H), and progression of HF. The impact of concomitant AF ( defined as any AF or AF on ECG) on these outcomes with and without BBB was analyzed. Results: 329 pts with HFpEF&amp;BBB were PS matched for 24 demographic&amp;disease state variables, BNP strata and AF status with a cohort of 329 pts with HFpEF without BBB. BBB was associated with increased risk of the TOPCAT primary outcome (Hazard ratio{HR} 1.44, 95% confidence intervals {CI} 1.10-1.89, p=0.008), increased risk of HF hospitalizations by 41%(HR 1.41 95% CI 1.04-1.91 p=0.0248) but not CVH (HR 1.18, 95% CI 0.93-1.49, p=..169), but not sudden death (HR 1.40, 95% CI 0.70-2.82, p=0.342) or CV death (HR 1.26, 95% CI 0.84-1.89, p=0.257). Risk of pump failure death (PFD) with BBB was significantly higher in HFpEF subjects without a history of AF (Figure left panel .Kaplan Meier Log rank p=0.0478, HR: 4.22, 95% CI: 0.89 to 19.87, p=0.0689) but not in AF (p=0.138). PFD risk was markedly higher in AF subjects without BBB ( Figure right, Kaplan Meier Log rank p=.0012, HR:7.99, 95% CI:1.80 to 35.41,p = 0.0063) than those with BBB (p=0.91) Conclusion: Ventricular dysynchrony induced by BBB independently worsens HFH risk in HFpEF. Its adverse impact on PFD iis seen in the absence of AF. Increase in PFD risk with AF in HFpEF subjects is most prominent in those with normal intraventricular conduction. Mechanical dyssynchrony induced by BBB may have a role in HFpEF subgroups with preserved atrioventricular filling, leading to these adverse HF outcomes

Abstract 4136989: Association of alternating PR intervals with paroxysmal atrioventricular block in patients with right bundle branch block following cardiac surgery

Background: We previously observed a positive correlation between QRS duration and the preceding RP interval in sinus rhythm in certain patients experiencing new onset left bundle branch block (LBBB) after transcatheter aortic valve replacement (TAVR). This unique phenomenon, termed inverse decremental conduction ( IDC ) or Yan conduction, prompted us to investigate whether IDC in the left bundle could manifest as AV conduction in an IDC pattern in patients with preexisting right bundle branch block (RBBB) and its association with atrioventricular block (AVB). Methods: 12 lead ECGs, available in-patient telemetry and mobile cardiac outpatient telemetry were reviewed in patients with sinus rhythm and preexisting RBBB who developed paroxysmal AVB requiring temporary or permanent pacemaker within 7 days following any types of cardiac surgery from 2014 to 2023 in Lankenau Medical Center. Results: A total of 9 patients (5 males) with a mean age of 71±15 years were identified to exhibit PR interval changes consistent with IDC prior to paroxysmal AVB. Among these patients, 6 had undergone TAVR, while the remaining 3 had undergone surgical aortic valve replacement, mitral valve repair, and ventricular septal defect repair, respectively. Specifically, PR interval alternation in the setting of RBBB occurred during sinus rhythm in a pattern that the longer RP interval is followed by a longer PR interval (Figure 1). This pattern exhibits the following features: 1) 8 of 9 patients had RBBB plus left anterior fascicular block (LAFB); 2) PR alternation occurred at sinus rates from 68 to 91 bpm within 5 days following surgical procedures; 3) proximal AVB occurred within 1 to 12 hours after PR interval alternation began. A positive correlation was established between PR and preceding RP interval in 2 of 9 patients whose telemetry data were available for analysis ( Figure 2A ). In a patient with RBBB who developed paroxysmal AVB without IDC changes in the PR interval post TAVR, intracardiac recording showed a decrease in AH interval but an increase in HV interval with slowing heart rates ( Figure 2B ), indicating that decremental conduction in AV node can mask IDC in Purkinje system. Conclusion: 1) PR alternation with longer PR following longer preceding RP interval in presence of RBBB, likely due to IDC in left bundle, heralds paroxysmal AVB; 2) PR interval changes resulting from IDC in left bundle in the setting of RBBB may be masked by decremental conduction in AV node.

Abstract 4137204: Classifying Left Ventricular Hypertrophy from ECG in Overall Population and Bundle Branch Blocks: Machine Learning Models are Superior to Published ECG Criteria

Background: Published ECG criteria for left ventricular hypertrophy (LVH) have low diagnostic yield, esp. with right/left bundle branch block (RBBB/LBBB). Machine learning (ML) may improve LVH classification. Hypothesis: ML performs better than published LVH criteria to classify LVH from ECG in overall population, and subgroups of RBBB/LBBB. Methods: In addition to standard ECG features like rates, intervals, axis etc., R, S and overall QRS amplitudes, and voltage-time-integrals were extracted from standard 12 leads and reconstructed vectorcardiographic X, Y, Z lead representative beats. Further, a variational autoencoder was used to extract latent encodings from the representative beats. ML algorithms (logistic regression, random forest, light gradient boosted machine, multilayered perceptron, residual network, and convolutional neural network) were trained to predict LVH (LV mass index women &gt;95, men &gt;115 g/m 2 ) from ECG features on a training set of adult ECGs and echocardiogram within 45 days of each other (general population N=240,476, RBBB n=22,110, LBBB n=12,563). We obtained ROC AUCs in a separate validation set for LVH classification by (a) individual ECG variables, (b) published LVH criteria and (c) ML models. Results: As shown in Tables 1-2 and Figure 1 , for LVH classification among the validation sets, AUCs were highest for ML models, intermediate for univariable models and least for published criteria (best ML model vs. best criteria: general population women 0.77 vs. 0.63, men 0.78 vs. 0.63; RBBB women 0.70 vs. 0.57, men 0.77 vs. 0.57; LBBB women 0.71 vs. 0.55, men 0.72 vs. 0.54). Conclusions: ML models perform better than published LVH criteria at classifying LVH from ECG in overall population, RBBB and LBBB.

Abstract 4145896: Terminal Rhythm of the Worldwide First Genetically Modified Porcine-to-Human Xenotransplantation

Background: The worldwide first genetically modified porcine-to-human cardiac xenotransplantation was successfully performed in January 2022 at the University of Maryland with the recipient surviving 60 days. Aim: Assess the ECG parameters and cardiac rhythm during the death of the worldwide first porcine-to-human xenotransplant. Methods: Continuous 6-lead ECG telemetry was used to analyze ECG parameters and cardiac rhythm during the final 9 minutes after withdrawal of life support. Results: At the time of withdrawal (W), the patient was in sinus rhythm (70bpm, PR interval 280ms, right bundle branch block (RBBB) with QRS 140ms, QT 400ms; Figure). PR prolongation up to 360ms with loss of P wave was noted at W+2:55min. Irregular junctional rhythm with blocked PACs and bradycardia (23 bpm) occurred around W+3:25min. At that time, widening of RBBB to 160ms with non-specific repolarization abnormalities and QT prolongation were observed. At W+4:30min, increasing pauses of up to 8.5s with mild QRS axis shift occurred. At W+6min, asystole (up to 20s) with rare PVCs from the left anterolateral LV base were seen. Final rhythm at W+6min consisted of ventricular escape beats from the infero-basal LV before electrical activity ceased at W+6:45min. No other atrial or ventricular arrhythmias were noted. Conclusion: The porcine-to-human cardiac xenotransplant showed a terminal rhythm of bradycardia, sinus arrest, and junctional and ventricular escape beats. This is consistent with ischemia-related failure of impulse generation, slowing intra-atrial/AV-conduction delay, and failure of impulse propagation. Notably, no tachyarrhythmias were seen despite ectopic atrial and ventricular beats with prolongation of depolarization and repolarization. This is similar to traditional terminal rhythms observed in humans and does not suggest unexpected arrhythmic proclivities between pig myocardium and the human environment (“pig heart in human body”).

Holter Monitoring Analysis of Women Infected with the Human Immunodeficiency Virus.

The aim of the study was to assess the clinical features of women infected with the human immunodeficiency virus (HIV) using Holter monitoring. Thirty-five female patients infected with HIV using a Holter monitor at the Ditan Hospital were retrospectively analyzed. In terms of basic rhythms, there were 30 cases of sinus rhythm, 27 cases of ventricular premature beat, 26 cases of supraventricular premature beat, 12 cases of mild reduction of HRV, 9 cases of normal heart rate variability (HRV), 8 cases of supraventricular tachycardia, 5 cases of abnormal ST-segment changes and 2 cases of sinus bradycardia 2 cases of paroxysmal atrial fibrillation 2 cases of junctional escape rhythm. There was only one case in each of the following ECG changes: persistent atrial fibrillation, sinus tachycardia, couplet supraventricular premature beats, accelerated idioventricular rhythm, sinoatrial block, second-degree Mobitz type I atrioventricular block, second-degree Mobitz type II atrioventricular block, complete right bundle branch block, T-wave abnormality, and significant reduction of HRV. The Holter monitor can show more changes in the electrocardiogram (ECG) of HIV-- positive patients, particularly significant ECG abnormalities, such as paroxysmal atrial fibrillation, and can direct early clinical treatment to serious adverse results.

Abstract 4138514: From Treatment to Trigger: A Case of Atomoxetine-Induced Brugada Pattern

Introduction: Brugada syndrome is an inherited cardiac disorder characterized by specific ECG patterns, notably the coved-type ST-segment elevation in the right precordial leads (V1-V3), leading to an increased risk of sudden cardiac death. This condition often stems from mutations in the SCN5A gene, which impair cardiac sodium channel function. The manifestation of Brugada Pattern, showing typical ECG findings without clinical criteria like sudden cardiac arrest or syncope, is significant. We highlight a case where atomoxetine, a selective norepinephrine reuptake inhibitor used for ADHD, unveiled a type 1 Brugada pattern. Case Presentation: A 26-year-old male with a history of ADHD on atomoxetine only presented to the emergency department with sudden substernal chest pain radiating to his left arm. His initial ECG showed right bundle branch block and type 1 Brugada pattern (Figure.1). Despite normal troponin levels and a negative coronary CT angiography, the patient's ECG abnormalities raised concerns. With no personal or familial history of arrhythmia or SCD and no other medications, atomoxetine was suspected as the trigger. Upon discontinuation, the patient's ECG type 1 Brugada pattern resolved (Figure. 2), and he remained asymptomatic with a normal Holter monitor at a 1-month follow-up. Discussion: Brugada syndrome is marked by dynamic ECG abnormalities, which can surface due to triggers like fever, certain medications, and electrolyte imbalances. Atomoxetine, an ADHD treatment and selective norepinephrine reuptake inhibitor, affects the human cardiac sodium channel (hNav1.5), encoded by the SCN5A gene. This interaction can disrupt heart action potentials, leading to conditions like long QT syndrome and Brugada pattern, by slowing cardiomyocyte depolarization and conduction. Its effect on hNav1.5 resembles that of antidepressants like Fluoxetine, increasing the risk of Brugada pattern. In our case, a patient's type 1 Brugada pattern, with no underlying heart disease or family history, pointed to atomoxetine as the cause. Discontinuing the drug resolved the ECG abnormalities. Conclusion: This case emphasizes the importance of assessing cardiovascular risk before prescribing atomoxetine, especially in individuals at risk for cardiac sodium channel dysfunctions. Immediate intervention and monitoring are critical to prevent severe arrhythmias.

Abstract 4138517: Role of Coronary Computed Tomographic Angiography in Patients with Discordant Findings on Exercise Stress Echocardiography

Background: Exercise stress echocardiography is routinely used for risk stratification and diagnosis of myocardial ischemia in low-to-intermediate risk patients with suspected coronary artery disease (CAD). Discrepancies between exercise electrocardiography (EKG) and echocardiography (ECHO) are common in clinical practice. Prior literature suggests that patients with discordant stress test results generally have worse outcomes, though the extent of epicardial atherosclerotic disease remains unclear. Coronary computed tomographic angiography (CTA) has gained a class I recommendation for the assessment of atherosclerotic burden per ACC/AHA chest pain guidelines. Using non-invasive fractional flow reserve (CT-FFR), the functional significance of lesions can also be assessed. This study investigates the incidence and burden of CAD in patients with discordant exercise echocardiography findings. Methods: Patients aged 18 or older who had exercise echocardiography followed by CTA from January 1, 2013, to January 31, 2023, were retrospectively enrolled in this study and categorized into two discordant result groups: EKG+/ECHO- or EKG-/ECHO+. Those who failed to achieve the target heart rate or had a paced rhythm/left bundle branch block on baseline EKG were excluded. CTA findings were classified as no CAD, non-obstructive CAD (&lt;50% stenosis), obstructive CAD (≥50% stenosis), and obstructive CAD with FFR+ (&lt;0.75). Results: The study included 198 patients, the majority female (56.0%), with a mean age of 61 ±10 years. Among them, 159 (80.3%) were EKG+/ECHO- and 39 (19.7%) were EKG-/ECHO+ (Table 1). In the EKG+/ECHO- group, 55 (34.6%) had no CAD, 48 (30.2%) had non-obstructive CAD, and 56 (35.2%) had obstructive CAD, out of which 19 (33.9%) were FFR+. In the EKG-/ECHO+ group, 13 (33.3%) had no CAD, 17 (43.6%) had non-obstructive CAD, and 9 (23.2%) had obstructive CAD of which 3 (33.3%) was FFR+. There was no statistically significant difference in the degree of CAD between the two cohorts. Conclusions: The majority of patients with discordant results on exercise echocardiography were found to have CAD. There was no significant difference in the degree of disease between the EKG+/ECHO- or EKG-/ECHO+ groups. Overall, discordant results on exercise echocardiography should not be discounted and warrant further evaluation. CTA provides important information that can impact the diagnosis and further medical management of patients with chest pain and suspected CAD.

Abstract 4120434: A Rare Case Of Localized Ventricular Tachycardia Due To Mitral Annular Disjunction And a Subvalvular Aneurysm

Introduction: Mitral annular disjunction (MAD) is an abnormality of the mitral valve where a portion of the mitral annulus and valve leaflets insert into the left atrium away from the fibrous annulus. Since its identification in 1981 its diagnosis has increased due to the advancements in cardiac imaging. It’s association with ventricular arrythmia (VA) and sudden cardiac death (SCD) underscores the importance of its identification. We present a case of ventricular tachycardia (VT) that is attributed to MAD with associated sub-mitral valve left ventricular aneurysm (SMA) formation. Case: A 51-year-old African American male with history of posterior papillary muscle premature ventricular contractions (PVC), PVC induced cardiomyopathy, and family history of sudden cardiac death in his mother who presented to the emergency department due to palpitations. Electrocardiogram (ECG) showed sustained monomorphic VT at a rate of 160 bpm. This converted to normal sinus rhythm with intravenous amiodarone and metoprolol. Further work up included cardiac magnetic resonance which identified a 4 x 1.8 x 1.4 cm SMA on the basal inferior and inferolateral walls. There was near transmural late gadolinium enhancement (LGE) of the aneurysm and an associated 7 mm of MAD with posterior mitral valve prolapse (MVP). He underwent left heart catheterization which was normal. ECG showed a superior right axis with associated right bundle branch block which correlated to a basal inferolateral exit and to the location of the SMA. Ultimately the patient underwent implantation of secondary prevention implantable cardioverter-defibrillator and initiation of sotalol. Discussion: The prevalence of MAD is approximately 30% in those with MVP and 8% in the general population. Those patients with MAD and MVP appear to be at higher risk for VA and SCD. The most likely mechanism for this association is the fibrotic changes that occur in the basal inferolateral left ventricle because of mechanical stretch on the papillary muscles by the prolapsing leaflets. The scar and aneurysm that develop can serve as substrate for reentrant VA. Treatment for this involves surgical repair of the mitral valve annulus and correction of the MAD distance which has been shown to improve arrythmia. Conclusion: This case illustrates an important but poorly understood arrhythmogenic entity that will increase in incidence as cardiac imaging advances. Its implications in VA and SCD warrant further research.

Abstract 4137975: 9-Year Longitudinal Assessment of the 12-lead Electrocardiogram of Volunteer Firefighters

Introduction: In the US, the most common cause of death among active-duty firefighters is sudden cardiac death (SCD). Underlying heart diseases are important propagator of ventricular tachyarrhythmias that cause SCD. The objective of this abstract is to assess the incidence of underlying heart disease, identified on 12-lead electrocardiograph (ECG), that may place firefighters at greater risk of SCD. Methods: We digitalized 12-lead ECGs recorded among firefighters who visited a firefighter health screening program at least 4 times from 2011-2019. We extracted the interval measurements (Heart Rate, T-axis, QRS-axis, QRS duration, QTc duration) and interpretation statements from each of the 12-lead ECGs and grouped potential propagators of ventricular tachyarrhythmias including left ventricular hypertrophy (LVH), coronary artery disease (CAD), and cardiac conduction disease. We used simple mean imputation to handle missing data. Descriptive statistics including means and frequencies were used to analyze the sample. Results: Among 465 firefighters (90.1% male) with a mean age of 47.1 (±13.6) whom 1,296 12-lead ECGs were analyzed, 21.5% (n=278) of Heart Rate, 0.39% (n=5) T-axis, 26.4% (n=342) QRS-axis, 40.0% (n=518) QRS duration, 5.40% (n=70) QTc duration were abnormal. In addition to intervals, the 12-lead ECGs generated 1,970 interpretation statements of which 28.2% (n=555) were deemed possible pathoanatomical substrates including 3.1% (n=34) LVH, 24.7% (n=137) CAD, and 69.2% (n=384) cardiac conduction diseases. Among cardiac conduction diseases, intraventricular conduction disease was the most prevalent (n=204, 36.8%), followed by vertical axis (n=70, 12.6%), right bundle branch block (n=59, 10.6%), left anterior fascicular block (n=34, 6.1%), and left bundle branch block (n=17, 3.1%). Interestingly, we did not observe a temporal relationship regarding the number of pathoanatomical substrates over the screening period. Conclusions: Nearly 30% of the interpretation statements generated from 12-lead ECGs were indicative of possible pathoanatomical substrates that cause SCD, which reflects the apparently negative effect of fire suppression activity on one’s cardiopulmonary health. Our result justifies the imperative need of effective prevention method for cardiac conduction diseases among firefighters. Further research is needed to collect 12-lead ECG systematically amongst other measures such as diet and BMI which reflect work culture and lifestyle of firefighters.

Abstract Su603: Out-of-hospital cardiac arrest presenting with ST-segment elevation myocardial infarction: Real world assessment and treatment

Background: Coronary artery disease is a common cause of out-of-hospital cardiac arrest (OHCA). Early recognition myocardial infarction (MI) and initiating appropriate therapy has been shown to improve outcomes in OHCA. While early coronary intervention is part of guidelines-based care, the implementation of these recommendation in actual US practice remains poorly described. Objectives: This study aims to characterize patients presenting with OHCA and MI in a cohort from 4 hospitals, to assess care of these patients in actual practice. Methods: We employed a database of OHCA patients admitted to four hospitals within the University of Pennsylvania Hospital System between 01/2019-12/2023. For this study, we included all patients that were diagnosed with STEMI during emergency department evaluation, and collected demographic, arrest, coronary angiographic, and ECG data from electronic health records. SAS was used for statistical analysis. Results: A total of 43 MI cases were included; mean age was 60.6±11.8 y, 65% male, mean BMI 30.0±6.3, 58.1% African American, 27.9% White or Caucasian, and 16.3% had a medical history of myocardial infarction. 74.4% were witnessed, and 44.2% received bystander CPR[BA1]. Initial shockable rhythm was present in 34.9%. 38 survived to hospital admission, and 9 were discharged alive. The first obtained 12-lead ECG (median time to ECG: 13min, (IQR: 3.5-26.5)) found that ST-segment elevations were present in 88.4%, ST-segment depressions in 44.2%, T-wave inversions in 4.7%, QT prolongation in 9.3%, and wide QRS in 18.6%. Sinus rhythm was most common (41.9%), followed by junctional rhythm (9.3%). Left and right bundle branch blocks (4.3% and 7%, respectively) and AV block (7%) were recorded. Coronary angiography (median time to angiography: 1.95hr (IQR: 1.3-4.2)) was performed in 29 patients and revealed that left anterior descending artery (28.6%) was the most common location for a culprit lesion, followed by the right coronary artery (21.4%), and left circumflex artery (10.7%). Notably, in 21.4% of cases, no culprit lesion was identified. 13 patients underwent angioplasty with stent, 4 received balloon angioplasty, and 1 underwent aspiration thrombectomy. Conclusion: This study highlights important attributes of OHCA patients presenting with MI. This paves the way for larger studies comparing ECG and coronary angiography findings between MI and control populations to help identify and improve acute care for OHCA MI patients.

Abstract 4140168: Association of left and right branch blocks with clinical outcomes in patients with heart failure with preserved ejection fraction (HFpEF)

Background: Although left (LBBB) and right (RBBB) bundle branch blocks play a critical role in cardiovascular pathogenesis, the associations of LBBB and RBBB with cardiovascular (CV) outcomes, especially in patients with HFpEF is understudied compared with normal QRS. Aim: We assessed clinical outcomes of LBBB and RBBB in patients with HFpEF who were admitted for acute decompensated heart failure compared with those without bundle branch blocks. Method: A cross-sectional study was conducted using the National Inpatient Sample (NIS) database from 2019. We only included adult hospitalizations with HFpEF admitted for acute decompensated heart failure in the study. Hospitalized records were categorized into three groups (LBBB, or RBBB, and those with normal QRS). Clinical outcomes included atrial fibrillation (AF), ventricular fibrillation (VF), complete heart block (CHB), sick sinus rhythm (SSR), cardiac arrest (CA), length of stay (LOS) and in-hospital mortality. Propensity score (PS) inverse probability of treatment weighting and matching were applied to determine the association between BBB types and CV outcomes and validated associations in sensitivity analyses. Results: A total of 334511 hospitalizations with HFpEF included LBBB (6818, 2%) and RBBB (7948, 2.4%) were analyzed. Compared to normal QRS, LBBB was associated with VF (odds ratio [OR]=2.47, p&lt;0.001), SSR (OR=1.72, p&lt;0.001), CHB (OR=2.77, p&lt;0.001) and longer LOS (relative risk [RR]=1.15, p&lt;0.001) after adjusting for covariates in PS analysis. Similarly, RBBB was associated with AF (OR=1.30, p&lt;0.001), VF (OR=1.59, p=0.033), SSR (OR=1.72, p&lt;0.001), CHB (OR=2.81, p&lt;0.001), CA (OR=1.19, p&lt;0.001), and longer LOS (RR=1.08, p&lt;0.001) [Table 1]. These associations remained consistent in multiple validation analyses including after additionally adjusting for obesity, hypertension and diabetes. Conclusion: In hospitalized records with acute decompensated HFpEF, BBB was associated with increased risk of CV outcomes and longer hospital length of stay. The extent of association with multiple CV outcomes varied according to RBBB and LBBB.

Abstract 4135061: Myocardial work in different patients with electrical dysynchrony due to left bundle branch block

Left bundle branch block (LBBB) in patients with dilated cardiomyopathy (DCM) is defined by huge wasted work and decreased myocardial constructive work. The aim of this study is to assess the myocardial work in patients in LBBB and other clinical situations. Materials and methods: The echocardiographic study was performed in 25 patients with LBBB and DCM (LBBB-DCM); 20 patients with DCM and narrow QRS complex (nonLBBB-DCM group); 15 patients with LBBB developed after transcatheter aortic valve implantation (TAVI group); 12 patients with idiopathic LBBB, normal systolic LV function and excluded cardiovascular pathology (LBBB group); 27 patients with right ventricular pacing due to atrioventricular block of high grade (RVP group) and 20 healthy volunteers (HV group). In all of them global longitudinal strain (GLS) and myocardial work parameters including global constructive work (GCW), global wasted work (GWW), global work index (GWI) and global work efficiency (GWE) were assessed. In all patients the segments with maximum and minimum GWI value were determined. Results: GLS, GWI and GCW values were comparable in LBBB and RVP groups, whereas in TAVI and in both DCM groups they was significantly lower than in HV (p = 0.049, 0.006, 0.025; p &lt; 0,001 respectively, (Fig.1A,B,C)). Patients from LBBB, TAVI, RVP and LBBB-DCM groups were characterized by increased amount of GWW (261 [203.5; 291.5], 273 [184.8; 385,3] and 237 [149.5; 445.3] vs 108 [74.3; 137.3] mmHg%, p = 0.033, 0.006, &lt; 0.001, &lt; 0.001 respectively). GWW value in LBBB-DCM group was the highest (346.5 [255.5; 437.8] mmHg% (Fig.1D). There was moderate strength of relation between GWW and QRS duration (ρ=0.456, p&lt;0.001). A huge amount of wasted work affected the GWE value and led to its considerable reduction in LBBB, TAVI, RVP and LBBB-DCM groups compared to HV (p = 0.033, 0.007, 0.023, &lt; 0,001, respectively, Fig.1E). The zone of maximum GWI localized in posterolateral wall, the zone of minimum GWI was in interventricular septum in most LBBB patients (Fig.1F). At the same time, these zones turned out to be very variable in RVP group. Conclusion: Although all patients with LBBB pattern of electrical activation are characterized by significant amount of wasted work, its contribution to global myocardial work manifested only in DCM patients. Wasted work doesn’t lead to reduced constructive work in patients with idiopathic LBBB and RVP and normal systolic function probably due to compensatory mechanisms.

Abstract 4125999: Elderly patients with HF with reduced ejection fraction and renal failure: are SGLT2i a good option?

SGLT-2 receptor inhibitors (SGLT-2i) have been shown to reduce cardiovascular mortality and hospitalisations for heart failure (HF) in patients with HF with reduced ejection fraction (HFrEF) and to have a nephroprotective role in patients with chronic kidney disease (CKD). However, the available evidence in patients older than 75 years and with CKD is limited. We conducted a retrospective, single-centre study including patients aged &gt;75 years diagnosed with HFrEF (defined as ejection fraction &lt;40%), CKD (eGFR &lt;60mL/min) and with an indication for treatment with SGLT-2i for HF between November 2019 and November 2022. Clinical, analytical, electrocardiographic and echocardiographic variables were collected. A total of 173 patients were included with a mean follow-up of 31.6 months (SD ±13.2). Mean age 84.7 years (SD ±4.9), 66.5% were male, 85.5% were hypertensive, 34.7% diabetic and 39.3% dyslipidaemic. Peripheral vascular disease was present in 11.6%. Mean glomerular filtration rate was 45.9 mL/min and only 2.3% were on haemodialysis. LVEF at inclusion was 29.5% (SD ±7.9), with 53.1% being of ischaemic aetiology and the most frequent functional class being NYHA II (53.2%). Thirty-seven percent had atrial fibrillation and 34.1% had complete left bundle branch block. At the end of follow-up 80.3% were on beta-blockers, 48.6% on ACE inhibitors, 37.6% on aldosterone antagonists, 23.7% on ARNI and only 11% on SGLT-2i. Survival analysis was performed using Cox logistic regression (multivariate analysis), where SGLT-2i was shown to be the only protective factor for all-cause mortality (HR 0.3 [0.1-0.9]). Male sex (HR 2.2 [1.3-3.9]) and diabetes (HR 1.6 [1.0-2.6]) were associated with higher mortality. The attached figure (figure 1) shows the Kaplan-Meier survival curves for total mortality in those patients with and without SGLT-2i (p log-rank 0.05). In our population, SGLT2i showed a significant reduction in total mortality in patients older than 75 years, with HFrEF and CKD. However, the treatment rate in this subgroup of patients is very low. Further implementation of SGLT2i treatment in this type of patient could be of significant clinical and prognostic benefit.

Abstract 4134305: Intraoperative indicators depending on QRS morphology are required to narrow QRS width during CRT implantation

Introduction: Various indicators to detect the most delayed electrical or mechanical activation site of left ventricular (LV) have been studied using intracardiac electrocardiogram or speckle tracking echocardiogram to narrow QRS width in patients with cardiac resynchronization therapy (CRT). Hypothesis: Unusual intraoperative indicators are required to narrow QRS width in patients with non-LBBB (left bundle branch block) during CRT implantation. Methods: Nineteen patients (14 men, 71±12yrs, 7 with left bundle branch block: LBBB / 10 non-LBBB / 2 pacing-depend, 6 ischemic cardiomyopathy, LVEF 29.6±8.9%, QRS 152±28ms) underwent CRT implantation. Q-LV (an interval from QRS onset to LV potential), RV-LV (from RV to LV), RVp-LV (from RV pacing to LV), and S-QRS (from LV pacing stimulation to QRS onset) were measured in multi-sites of coronary sinus (CS) veins using a 5 mm spacing 2Fr 8-polar catheters. Q-peak strain (an interval from QRS onset to peak radial strain) was evaluated by speckle tracking echocardiogram in each LV segment during sinus rhythm (SR) and RVp. QRS narrowing was defined as the difference between the QRS interval during SR (or RVp) and the QRS interval with biventricular pacing. Results: Parameters were evaluated in 17±7 (8-32) sites of 1.9±0.9 (1-4) CS branches in each patient. In LBBB patients, longer Q-LV during SR, extended RV-LV during SR, and lengthy Q-peak strain during SR were associated with QRS narrowing. Shorter S-QRS during LVP and longer RVP-LV during RVP were related to QRS narrowing in non-LBBB patients. (Table) Conclusion: Suitable indicators depending on QRS morphology are required for QRS narrowing in CRT implantation. The parameters using speckle tracking echocardiogram to detect mechanical LV delay sites might not be useful in patients with non-LBBB.

Abstract 4114276: Identification of the heterogeneity in the risk of heart failure in those with left bundle branch block pattern using artificial intelligence

Introduction: The association between left bundle branch block (LBBB) and heart failure is well-established. However, the lack of a practical risk assessment tool for patients with LBBB poses a clinical challenge to the management despite the heterogeneity of the LBBB population. Hypothesis: Artificial intelligence (AI) can extract features to stratify the risk of heart failure (HF) within the heterogeneity of LBBB. Methods: All 12-lead ECGs diagnosed with LBBB recorded from 1/1/2015 to 12/31/2019 were identified in our institution. ECG data were analyzed as 2D matrices with a shape of 12×2500. The Uniform Manifold Approximation and Projection (UMAP) was used to visualize the heterogeneity of LBBB ECG. Additionally, a 2-dimensional convolutional neural network model was trained to detect LBBB ECGs associated with past HF diagnosis. The model was then applied to ECGs from an external cohort of patients with LBBB but without a history of HF. Cumulative incidences of HF admission were compared by stratifying according to tertiles of the model output (low, intermediate and high AI score groups) Results: We identified 15,124 LBBB ECGs in our institution (training dataset) and 2,463 individuals with LBBB ECGs in the external cohort (external test dataset). The UMAP projection of the ECGs revealed distinct heterogeneity in the data ( Fig A ). This heterogeneity was not fully explained by patient demographics, ECG features, or institutions. When the external cohort was divided into 3 groups according to the tertile of AI prediction, patients with high AI scores had a higher risk of HF admission (high vs low AI score group: hazard ratio (HR), 2.10; 95% confidence interval (CI), 1.66-2.65; intermediate vs low AI score group: HR, 1.39; 95%CI, 1.08-1.78: log-rank p &lt;0.0001; Fig 1B ). This finding was unchanged after adjusting for multiple clinical characteristics and ECG parameters, including QRS duration. Conclusion: We observed significant heterogeneity in ECGs presenting LBBB, and the AI model excellently stratified the risk of heart failure admission in patients with LBBB from a single recording of 12-lead ECG, suggesting great potential for clinical utility in managing patients with LBBB.

Abstract 4135080: Relation of focal and diffuse myocardial fibrosis to left bundle branch block in patients with dilated cardiomyopathy and structurally normal heart

The role of fibrosis in etiology of left bundle branch block (LBBB) in still not defined. The aim of this study was to assess the relation of focal and diffuse LV fibrosis to LBBB in patients with dilated cardiomyopathy (DCM) and in patients with structurally normal heart. Materials and methods: 60 DCM with LBBB (DCM-LBBB group, 46.7% male, mean age 57[50;63] years), 50 non-LBBB DCM (78% male, mean age 43[32.3;54] years), 15 patients (53.3% male, mean age 39[28;50] years) with LBBB and no signs of structural heart disease and 10 healthy volunteers (HV) were included in the study. Endomyocardial biopsy (EMB) was performed in 15(24,6%) LBBB-DCM and 16(32%) non-LBBB DCM patients and allowed the quantification of collagen volume fraction (CVF, Fig.1A-D). All patients and HV underwent cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE) analysis. Obtained LGE LV images were post-proceed for core scar (CS) and gray zone (GZ) calculation and 3D reconstruction. Diffuse LV interstitial fibrosis was estimated on all LGE-CMR images with the novel introduced marker - diffuse intensity ratio (DIR). Results: DIR was validated on EMB samples: the percentage of CVF (8.2[4.6;10.8]%) correlated with the DIR value (0.71 ± 0.13) in the same segment (r=0.66, p&lt;0.001, Fig.1E-F). The value of CVF (Fig1A-D) and LGE presence in the septum in both DCM groups (Fig2) was comparable (8.2[4.6; 10.3] versus 7.6[6.1;15.3]%, p=0.82 and 19 (31.7%) versus 17 (34%) patients in non-LBBB DCM group respectively, p=0.8) Moreover, the presence of LGE and midwall fibrosis in septum was not related to the QRS duration (p=0.93 and 0.59). In non-LBBB DCM patients the percentage of CS was significantly higher (4.0[1.55; 11.68]% versus 1.4[0.05;8.5]% in LBBB-DCM patients, p=0.047), whereas percentage of GZ and total fibrosis in both DCM groups was comparable (Fig.3A,B). DIR value was higher in patients with idiopathic LBBB than in HV (0.54±0.09 versus 0.34±0.1, p&lt;0.001) while the percentage of GZ and CS was extremely low and did not differ from its amount in HV (Fig.3C,D). Conclusion: Neither focal (including midwall striae) nor interstitial fibrosis is associated with LBBB in patients with DCM. Diffuse inflammation in LBBB-DCM patients may contribute to the progression of systolic dysfunction but is not the reason for LBBB. The increased value of interstitial fibrosis in patients with LBBB may reflect latent diffuse process in myocardium inexorably leading to DCM development.

Derivation and internal validation of prediction models for pulmonary hypertension risk assessment in a cohort inhabiting Tibet, China.

Individuals residing in plateau regions are susceptible to pulmonary hypertension (PH) and there is an urgent need for a prediction nomogram to assess the risk of PH in this population. A total of 6603 subjects were randomly divided into a derivation set and a validation set at a ratio of 7:3. Optimal predictive features were identified through the least absolute shrinkage and selection operator regression technique, and nomograms were constructed using multivariate logistic regression. The performance of these nomograms was evaluated and validated using the area under the curve (AUC), calibration curves, the Hosmer-Lemeshow test, and decision curve analysis. Comparisons between nomograms were conducted using the net reclassification improvement (NRI) and integrated discrimination improvement (IDI) indices. NomogramI was established based on independent risk factors, including gender, Tibetan ethnicity, age, incomplete right bundle branch block (IRBBB), atrial fibrillation (AF), sinus tachycardia (ST), and T wave changes (TC). The AUCs for NomogramI were 0.716 in the derivation set and 0.718 in the validation set. NomogramII was established based on independent risk factors, including Tibetan ethnicity, age, right axis deviation, high voltage in the right ventricle, IRBBB, AF, pulmonary P waves, ST, and TC. The AUCs for NomogramII were 0.844 in the derivation set and 0.801 in the validation set. Both nomograms demonstrated satisfactory clinical consistency. The IDI and NRI indices confirmed that NomogramII outperformed NomogramI. Therefore, the online dynamic NomogramII was established to predict the risks of PH in the plateau population.